Prediction of time-to-delivery (TTD) is clinically important among pregnancies at risk for preterm delivery, particularly in regard to administration of corticosteroids (which have optimal benefit within 24 hours to 7 days of administration). In addition, patients at high risk for preterm birth should deliver in a tertiary care unit. Obstetricians are tasked with predicting TTD in patients at risk for preterm delivery, particularly given the controversy over the use of repeated steroids.
The American College of Obstetricians and Gynecologists (ACOG) indicates in its most recent Practice Bulletin on the Management of Preterm Labor that, while many tests to identify women at risk of preterm birth have been proposed and evaluated, only ultrasonography (to determine cervical length) and fetal fibronectin testing have been shown to have benefit. Ultrasonography or fetal fibronectin testing, or a combination of both, may be useful in identifying women who are at high risk for preterm delivery. However, their clinical usefulness may rest primarily with their ability to identify women who are least likely to deliver (i.e., the tests' negative predictive value (NPV)), not women who are most likely to delivery (i.e., a test with a high positive predictive value (PPV)). Thus, there is an urgent need for a test with a high PPV in order to accurately predict imminent delivery, and to allow for salutary intervention.